diff --git a/src/core/file_sys/vfs.h b/src/core/file_sys/vfs.h
index 3bbc361ba..78a63c59b 100644
--- a/src/core/file_sys/vfs.h
+++ b/src/core/file_sys/vfs.h
@@ -36,7 +36,7 @@ enum class VfsEntryType {
 // functionality, they will need to override.
 class VfsFilesystem : NonCopyable {
 public:
-    VfsFilesystem(VirtualDir root);
+    explicit VfsFilesystem(VirtualDir root);
     virtual ~VfsFilesystem();
 
     // Gets the friendly name for the filesystem.